London Marathon chief executive Hugh Brasher said discussions are ongoing over a proposal to stage a one-off two-day marathon in 2027, with elite women racing on the Saturday and men on the Sunday, but stressed no final approval has yet been secured.
The landmark race, which marks its 46th edition on Sunday, is in talks with multiple stakeholders about the feasibility of splitting the event across two days, Brasher said on Wednesday.
"We have lots of plans," the CEO of London Marathon Events told reporters. "And we do have multiple stakeholders and we are, and have been, engaging with them for a long period of time.
"There are conversations going on this week, next week. We do hope we will get signed off, but it is a huge undertaking, not only from our team's point of view, but also London's point of view," he added.
Brasher said the complexity of the capital's sporting calendar was a key factor in the discussions, pointing to major events already scheduled for the same weekend in 2027.
"On that day, you will have an FA Cup semifinal on the Saturday and the Sunday 2027 is a packed sporting calendar for London, with the Tour de France Femmes coming," he said.
If approved, the two-day format would be staged only once, Brasher said.
"It absolutely is a one off," he said. "We think that this should be properly explored, which is what we've been doing for some time. And we hope that we get to a position where we can announce it."
Brasher pointed out that research from Sheffield Hallam University found that a two-day London Marathon could raise over £130 million for charity and generate £400 million in economic benefits.
The 2025 London Marathon raised a record £87.3 million for charity, cementing its status as the world's largest annual one-day fundraising event.
Approximately 59 000 runners are expected to cross the finish line of Sunday's 42.195-kilometre race in what would be a world record.
Last year's edition saw 56 640 people cross the finish line, setting a Guinness World Record for largest number of finishers in a marathon.
Brasher predicted some "mouth-watering elite races to watch" on Sunday.
"My personal favourite for once, it's normally been the women's, I think for once it is going to be the men's race," he said.
"Sebastian Sawe (the defending champion), Jacob Kiplimo, Joshua Cheptegei in his (marathon) debut, and Tamirat Tola as the Olympic champion, I think it's going to be an incredible race."
The women's field features defending champion Tigst Assefa, plus New York Marathon champion Hellen Obiri.